Apparatus and method for cooling metal slabs with a unitary structure for depositing and grasping the slabs

ABSTRACT

An apparatus and method for transporting metal slabs into and from a cooling basin comprises, on a carriage movable longitudinally of the basin, a unitary slab grasping device including a plurality of grasping devices spaced apart transversely of the basin, each of which devices forms two sideby-side downwardly opening pockets for alternately receiving a slab and is provided with a retainer member for releasably latching a slab in either pocket. The carriage is moved to a slab feed station at one end of the basin, where a hot slab is fed into and grasped in one of the pockets; thence along the basin to a location where the grasping device is lowered into the basin and is operated both to deposit the hot slab into an empty compartment of the basin and grasp in the other pocket a cooled slab present in an adjacent compartment. The grasping device then is raised and the carriage is moved farther to discharge the cooled slab at the other end of the basin. The retainer may comprise for each grasping device a member movable to close the bottom of either pocket or a separate retainer member for each pocket.

United States Patent [191 Manthey et al.

[451 July 22, 1975 APPARATUS AND METHOD FOR COOLING METAL SLABS WITH AUNITARY STRUCTURE FOR DEPOSITING AND GRASPING THE SLABS [75] Inventors:Willi Manthey, Duisburg; Horst Deiwick, Krefled, both of Germany [73]Assignee: BWG-Bergwerk-und Walzwerk Machinenbau G.m.b.H., Duisburg,Germany [22] Filed: Oct. 13, 1972 [21] Appl. No.: 297,470

[30] Foreign Application Priority Data Nov. 24, 1971 Germany 2158091[52] U.S. Cl. 62/64; 72/201; 134/25 A; 134/76; 134/134; 214/658; 266/4A; 294/67 [51] Int. Cl B66f 9/18; B65g 47/34 [58] Field of Search 134/25A, 42, 76, 77, 133, 134/134, 140, 164; 266/4 A, 6 R; 72/201;

214/1 BC, 658; 198/33 AD; 148/153, 155,

157; 294/67 R, 87 R, 67 D, 26.5, 69 R; 62/64 Primary Examiner-S. LeonBashore Assistant Examiner-M. Steven Alvo Attorney, Agent, or FirmAlbert C. Johnston [57] ABSTRACT An apparatus and method fortransporting metal slabs into and from a cooling basin comprises, on acarriage movable longitudinally of the basin, a unitary slab graspingdevice including a plurality of grasping devices spaced aparttransversely of the basin, each of which devices forms two side-by-sidedownwardly opening pockets for alternately receiving a slab and isprovided with a retainer member for releasably latching a slab in eitherpocket. The carriage is moved to a slab feed station at one end of thebasin, where a hot slab is fed into and grasped in one of the pockets;thence along the basin to a location where the grasping device islowered into the basin and is operated both to deposit the hot slab intoan empty compartment of the basin and grasp in the other pocket a cooledslab present in an adjacent compartment. The grasping device then israised and the carriage is moved farther to discharge the cooled slab atthe other end of the basin. The retainer may comprise for each graspingdevice a member movable to close the bottom of either pocket or aseparate retainer member [56] References Cited f h k UNITED STATESPATENTS or eac 3,680,344 8/1972 Manthey et a1. 72/201 7 94 DrawingFigures 4 .9 /0 Q 7 B 3 H Li H i] l l s .11 ill! :i ll!- 21 1 eeee 96996969 eeee g 30 PATENTEDJUL 22 ms .SHEET III tem for depositing the slabsinto and removing them from an elongate cooling basin.

This invention is particularly useful as an addition'to and improvementof a slab cooling system of the typedisclosed in US. Pat. No. 3,680,344,issued Aug. l,

1972, for an invention of Willi Manthey and Heinz Schmitter. In such asystem, slabs or similar semi--' finished products of iron-works or thelike are cooled by immersion in a cooling liquid such as water held inan elongate basin having a rectangular cross-section and provided with ashelf-like frame which forms bays or compartments therein to receive theslabs. Slabs are disposed in the cooling basin in an upright on-edgeposture by means of a transporting device which extends transverselyover and is movable along the basin and is equipped with a slab holder,or grasping means, movable vertically into and out of the cooling basin.The frame in the basin comprises longitudinal supports and verticalprongs which form compartmens lying transverse to the cooling basin. Thetransporting device is movable on rails longitudinally of the coolingbasin between slab feeding and discharge stations at opposed ends of thebasin. The slab grasping means comprises spaced apart grippers, orgrasping devices, each of which has the form of a double-bar pocketopening downwardly'and provided with a retaining member for closing itsbottom so as to latch a slab in the pocket. The retaining member ismoved by a control rod into closed and open positions.

According to the disclosure of the aforementioned patent, the graspingmeans of the transporting device constitutes one slab retaining pocket.If only one transporting'device is used, the same grasping means mustfirst lower and release a hot slab and then, by further" vertical andhorizontal displacements of it, grasp and remove a cooled slab. Thus,only a relativelylow con-- veying frequency can be obtained. If, on theother hand, two transporting devices are used, their operatingeffectiveness is impaired because of an overlappingof the conveyingdistances.

This invention has as its object to provide a new and improved slabtransporting system for an apparatus of the kind described, whichenables rapid and troublefree conveyance for the lowering of hot slabsinto and removing of cooled slabs from a cooling basin.

In accordance with this invention, the slab grasping means onthecarriage movable along the cooling basin constitute two downwardlyopening pockets in parallel side-by-side relation and are provided withretaining means selectively operable upon each disposition of thegrasping means in the basin to release a hot slab from one of thepockets into a vacant compartment of the basin and to latch in the otherof the pockets a cooled slab present in a basin compartment adjacent tothe previously vacant one. The slab grasping means constitute the twodownwardly opening pockets in aunitary structure that is movable as aunit into andout of the basin by vertical movement of thisstructure'relative to the carriage.

them of the slab grasping means into and then out of the basin, lowerahot slab into a vacant compartment and grip and lift out of the basin acooled slab present in the adjacent compartment. The removed slab canthen be carried to the delivery station.

Thus, it becomes possible during each trip from the slab feeding stationto the discharge station to lower or set downa hot slab and take out acooled slab and carry it away; and an especially favorable transportingsequence can be achieved. Upon each working trip of the carriage alongthe cooling basin 'a hot slab may be placed in the pocket emptied duringthe preceding trip. As a consequence, the process of depositing in onecompartment and emptying an adjacent compartment proceeds compartment bycompartment over the entire length of the cooling basin, and each slabremains in its compartment for a period determined by the time taken fora cycle of the carriage movements and the number of compartments in thecooling basin, until it is removed in the regular sequence of operation.

The double pocketed grasping means of apparatus according to thisinvention can be provided with any of various means for releasablyretaining a slab in either of the pockets. In one arrangement, thecentral vertical wall? separating the two pockets of each grasping unit'has' at' the bottom thereof a pivoted bearing connected in asubstantially horizontal path of about to' and from either of twoworking positions. In one of these positions the retaining memberextendsacross the bottom of and will hold a slab in one of the pockets,and in the other it functions similarly for the other pocket.

In another arrangement, a separate retaining member is provided for eachpocket, as by hinging such a member at the bottom of each of the twoouter bars which border the pockets. Each retaining member may be moved,as by a suitable control rod, to and away from alclos ed position inwhich it extends across the bottom of and will hold a slab in therelated pocket. The bottom portion of the central bar in thisarrangement may be provided with a recess to receive and a ledge tosupport an end portion of each retaining member.

The apparatus according to this invention may be givenl an even greatercapacity by utilizing a cooling basirijl'iaving therein two slabpositioning frames arranged side by side and along the basin so that twogroups of slabs may be treated simultaneously. The earriage spanning thewidth of the basin is then provided with two sets of slab grippers,-orgrasping devices, comprising at least four of these devies. Each ofthese grasping devices forms two pockets in parallel side-bysiderelation as above described. This design has the advantage that twoslabs can be set down simultaneously with an end of one slab near to anend of the other, in a plane transverse to the longitudinal axis of thecooling basin; yet only onetransporting means is required. An apparatusgiven this doubled capacity can also be used for individual slabs whichhave up to twice the length of the slabs for which each slab positioningframe in the basin is designed.

By virtue of this arrangement, a transporting device 3 according to theinvention can, by a single displace The above mentioned and otherobjects, features and advantages of the invention will be furtherapparent from the following detailed description and the accompanyingdrawings of illustrative embodiments thereof.

in the drawings:

FIG. 1 is a longitudinal sectional view of a preferred embodiment of acooling system provided according to this invention;

FIG. 2 is a transverse cross-sectional view of the cooling basin,carriage and slab grasping means of the system of FIG. 1; I

FIG. 3 is an enlarged detailed vertical sectional view of a unit of thegrasping means, taken in the longitudinal direction of the coolingbasin; and

FIG. 4 is an enlarged detailed vertical sectional view of anotherembodiment of slab grasping means according to the invention.

The cooling system according to the embodiments illustrated makes use ofan elongated cooling basin 6 having vertical end and side walls 7. Thecooling basin may have a rectangular cross-section. Two slab positioningframes each consisting of longitudinal supports 8 and verticallyextending prongs 9 are disposed within the basin 6. Each positioningframe may have at least two longitudinal supports 8 which define a shelfand to which the prongs 9 may be fastened. The prongs 9 are spaced apartin the longitudinal direction of the basin so that they formcompartments to receive slabs disposed vertically between successiveprongs ancl supported edgewise on the shelf defined by the supports. Theshelves of both positioning frames are aligned relative to each other inthe same, generally horizontal plane.

The cooling basin 6, as is well known in the art, may be filled with acooling liquid such as water and have a circulation system (not shown).Two parallel rails 10 (FIG. 2) extend along the opposite longitudinaledges of the side walls 7 of the basin. A transporting device orcarriage 11 is movably supported upon the rails 10. The carriage 11comprises a frame 12 which extends over the full width of the coolingbasin 6. On the frame 12 are mounted hoists 15. The hoists 15 compriserack and pinion gears 15a for raising and lowering a traverse 13. Fourdoubly pocketed grasping devices 14 more fully described hereinafter,are mounted on the traverse 13. The carriage 11 is movablelongitudinally of the cooling basin 6 on wheels which ride upon therails 10.

Each slab grasping device 14 comprises three parallel vertical bars, orwalls, 17, 18 and 19, respectively, which between them form two mutuallyparallel, downwardly opening pockets 16. The walls 17, 18 and 19 have aheat insulating lining 24, preferably made of an asbestos platematerial, over their inner surfaces. At the bottom of the pockets areretaining means operable to latch and support a slab releasably ineither pocket.

In the embodiment of FIG. 3 the retaining means comprise a member 22which is positioned by a rotatable control rod 20 arranged in thecentral bar 18. The control rod 20 is coupled to a bearing 21 pivoted ina bottom portion of the central bar 18 and a retaining member 22 isfitted in this pivoted bearing 21. The re-,

taining member 22 is formed with a shape and dimensions emabling it toextend across the bottom of either of the pockets l6 and thus securelyto latch and support a slab in the pocket, and it is movable selectivelyinto and away from this closed position with respect to either of thepockets. To that end, the bearing 21 has an opening in which the member22 is hinged and from which member 22 extends horizontally so that itcan be turned through a path of approximately 180 from the bottom of onepocket to the bottom of the other by rotation of the control rod 20. Thetwo outer or side bars 17 and 19 of the grasping device each has arecess in registry with the bearing opening, and has a ledge 23 whichforms a seat for the front end of the retaining member 22. The uppersurface of the retaining member 22 .is provided with a heat insulatinglining 24 which preferably is an asbestos plate material.

The rotatable control rod 20 may be connected through suitable gearingto a hydraulic or electric drive (not shown). The drive may be operatedas a function of the particular work cycle desired and may dispose theretaining member 22 in the latching or closed position for either of thepockets 16 or in an intermediate open position.

Referring now to another emobodiment, there is shown in FIG. 4 a slabgrasping device 14 having a separate retaining member 27 for each pocket16. Each retainer 27 is hinged on a horizontal axis and has on its backend a lever arm pivotally secured to the lower end of a verticallymovable control rod 26. By means of its control rod 26 each member 27may be disposed in a closed position in which it extends across thebottom of its pocket and is supported at its front end by a laterallyextending ledge 28 provided at the lower end of the central bar 18 belowa recess in that bar. On the other hand, each member 27 can be pivotedupwardly to an open position, as shown in relation to bar 19 in FIG. 4,so that the pocket 16 is open to receive or release a slab 1 (shown bydot-dash lines in the closed pocket 16 in FIG. 4). The rods 26 areconnected with a suitable hydraulic or electric driving means (notshown) which, in turn, is actuated as a function of the particularworking cycle desired so as to dispose each of the retaining members 27in either its closed or its open position.

As more fully described in the aforementioned patent, a pivotal hoistdevice 4 is provided at the slab feeding station at the front end of thecooling basin 6, and a pivotal unloading device 29 is provided at theslab discharge station at the other end of the basin. A hot slab to becooled is rotated by the device 4 through from a flat-lying into anupright on-edge position.

Each cooled slab is re-positioned in reverse manner by the device 29.The hot slabs 1 may be conveyed to the feeding station by means of aconventional roll train 2. A pusher 3 pushes the slab 1 into the hoistdevice 4. The device 4 then is pivoted by hydraulic means 5 about anaxis 5 so that the slab 1 is moved from a flat to an upright position sothat it may be grasped in a pocket of the grasping devices 14 oncarriage 11 at the feeding station. At the delivery end, on the otherhand, a cooled slab 1 is inserted, by means of the grasping devices onthe carriage 11, into the lowering device 29 which is then pivoted 90about axis 30 to lay the slab flat in a horizontal position. The slab isthen pushed by means of a pusher (not shown) onto a lowering platform 31which then depositsthe slab on a conveying device such as a roll train(not shown). The devices 4 and 29 may be arranged, in side-by-side pairsat the two ends of the cooling basin 6 so that two hot slabs may besimultaneously taken up by the carriage 11 and two cooled slabssimultaneously set down.

In operation, two hot slabs 1 are removed from roll train 2 and pushedinto the hoist devices 4 by a pusher 3. Following that, the devices 4are pivoted to place the slabs in a vertical posture. The carriage 11now takes up the two slabs in a pocket 16 of the grasping devices 14,these devices being lowered by means of the rack and pinion 'drive and15a to dispose an empty pocket 16 in each 'of them over one'of the slabsand the corresponding retaining member 22' theri'bein'g moved into itslatching position by means of a control rod (see FIG. 3). Followingthat, the grasping devices are raised together with the latched-iiislabe 1. i

The carriage 11 is now moved along the cooling basin 6 to a locationthereover where an empty'cooling compartment exists to receive the hotslabs" in the carriage. While the carriage is at this location, thegrasping-devices 14 are lowered into thebasin so as to-placethe hotslabs in the empty compartment: i.e., each slab being disposed betweentwo adjacent paris of prongs 9 and supported upon longitudinal supports8. During this lowering, the bottom of the other, unoccupied pocket 16of each grasping device .14 i's'open so that each of these vacantpockets is moved-over a slab present in a compartment of the basinadjacent tov thecompartment .into which a. hot slab is being deposited.When the hot slabs have been lowered onto the longitudinal supports 8,the grasping devices 14 are lowered below thesupports 8 sufficientlythat their retaining members 22 (under the hot slabs), beingof the typeshown in FIG. 3, may now be rotated 180 to a position underlying thecooled slabs in the pocket placed over them. Then, the grasping devices14 are raised back up into the carriage with the cooled slabs latchedtherein, after which the carriage 11 is moved farther along the basin tothe delivery station. The slabs are then lowered by the grasping means14 and inserted into the unloading device 29.

After the slabs are released from the grasping means 14 and into theunloading device 29, that device is rotated 90 and the slabs are pushedonto the lowering platform 31. The carriage 11 now proceeds back to thefeeding station for a repetition of the aforedescribed process. The newhot slab (s) is now deposited in the compartment (s) that was emptied inthe preceding cycle. In this way, the location at which the graspingmeans deposit a hot slab and pick up a cooled slab progresses steadilyfrom one end to the other of the cooling basin. A prerequisite is thatat the start and end of each cycle there is an empty compartment.

The grasping devices 14 are operated as a function of the particularworking cycle desired. When they are moved to the feeding station totake up a hot slab, their retaining members 22 or 27 are in the openposition. When then they are moved over the slab, and after encompassingit, the respective members 22 or 27 are disposed in the locked position.At the same time, however, the adjacent pocket is in the open condition.Thus, as the hot slab is lowered into the basin, the vacant pocket beinglowered with it can at one and the same time encompass a cooled slab.Then, after the hot slab is lowered, the members 22 or 27 are removedfrom under the deposited hot slab and the same or like members are inturn brought into latching position underneath the cooled slab in theadjacent pocket 16. The

riage 11 can, instead of transporting two slabs at a time, i

move only one at a time, the length of which can be as great or aslittle as may be accommodated in the compartments of the cooling basin.

What is claimed isf lqIn apparatus for cooling metal slabs such as hotbars, bill'ets, blooms or ingots, comprising an elongate basin for acooling liquid, slab feeding and slab discharge stations respectively atopposite ends of said basin, rneans forming in and longitudinally ofsaid basin a succession of upwardly open compartments each extendingtransversely of said basin for supporting therein a slab placedvertically therein, a carriage disposed transversely 'over'said basin,means mounting said carriage for movement longitudinally of said basinbetween said stationsf slab grasping means on said carriageand means'fordisplacing said grasping means vertically relative to said'carriage soas to move slabs successively into and out of said compartments, theimprovement wherein said slab grasping means includes a unitarystructure movable as a unit into and out of said basin and constitutingtwo downwardly opening pockets in parallel side-by-side relation, eachfor'receiving at least one of said slabs, and retaining meansselectively operable upon a single disposition of said grasping means insaid basin to release a hot slab from one of said pockets into a vacantone of said compartments and to latch in the other of said pockets acooled slab present 'in one of said compartments adjacent to said vacantone.

2. Apparatus according to claim 1, said grasping means comprising aplurality of slab grasping devices spaced apart transversely of saidbasin, each of said devices comprising a central vertical bar and twoouter vertical bars spaced horizontally from said central bar, said barsdefining said pockets therebetween, said retaining means comprising oneach of said outer bars a retaining member pivotally mounted formovement to and away from a closed position in which said member extendsacross the bottom of and will hold a slab in the related pocket.

3. Apparatus according to claim 2, said central bar having in the lowerportion thereof a recess to receive and a ledge to support an endportion of each of said retaining members.

4. In apparatus for cooling metal slabs such as hot bars, billets,blooms or ingots, comprising an elongated basin for a cooling liquid,slab feeding and slab discharge stations respectively at opposite endsof said basin, means forming in and longitudinally of said basin asuccession of upwardly open compartments each extending transversely ofsaid basin for supporting therein a slab placed vertically therein, acarriage disposed transversely over said basin, means mounting saidcarriage for movement longitudinally of said basin between saidstations, slab grasping means on said carriage and means for displacingsaid grasping means vertically relative to said carriage so as to moveslabs successively into and out of said compartments, the improvementwherein said slab grasping means constitute two downwardly openingpockets in parallel side-byside relation, each for receiving at leastone of said slabs, and retaining means selectively operable upon asingle disposition of said grasping means in said basin to release a hotslab from one of said pockets into a vacant one of said compartments andto latch in the other of said pockets a cooled slab present in one ofsaid compartments adjacent to said vacant one, said grasping meanscomprising a plurality of slab grasping devices spaced aparttransversely of said basin, eahc of said devices comprising a centralvertical bar and two outer vertical bars spaced horizontally from saidcentral bar, said bars defining said pockets therebetween, saidretaining means comprising a retaining member pivoted on an axis in saidcentral bar for rotation selec tively to either of two working positionsin one of which said member extends across the bottom of and will hold aslab in one of said pockets and in the other of which it extends acrossthe bottom of and will hold a slab in the other of said pockets.

5.- Apparatus according to claim 4, said retaining member beingrotatable about said axis in a substantially horizontal path ofapproximately 180 from one to the other of said positions, whereby aslab may be re leased from one of said pockets 'and another slab latchedin the other of said pockets by a rotation of said member.

6. Apparatus according to claim 4, each of said outer bars having arecess therein to receive, and forming a ledge to support, the outer endportion of said retaining member. I v

7. The method of transporting metal slabs into and from a cooling basinwhich comprises a. moving a carriage having slab grasping means thereonin steps from a slab feeding station at one end of an elongate coolingbasin to the location of a vacant compartment and an adjacentslabcontaining compartment in a succession of slab cooling compartmentsprovided in and along said basin, next from said location to a slabdischarge station at the other end of said basin, and then back to saidfeeding station for a next series of such steps, said grasping meansconstituting two downwardly opening slab receiving pockets in parallel,side-by-side relation; I i

b while said carriage is at said feedingstation placing and latching ahot slab in one only of said pockets;

c. while said carriage is at said location; lowering said grasping meansinto said basin so as to place said hot slab in said vacant compartmentand to place the. other ofsaid pocketsin encompassing relation to acooled slab in said slab-containing compartment, then releasing said hot,slab from said one pocket and latching said cooled slab in said other Ipocket, and then raising out of said basin said grasping means with onlysaid cooled slab held leasing said cooled slab from saidother pocket.

1. In apparatus for cooling metal slabs such as hot bars, billets,blooms or ingots, comprising an elongate basin for a cooling liquid,slab feeding and slab discharge stations respectively at opposite endsof said basin, means forming in and longitudinally of said basin asuccession of upwardly open compartments each extending transversely ofsaid basin for supporting therein a slab placed vertically therein, acarriage disposed transversely over said basin, means mounting saidcarriage for movement longitudinally of said basin between saidstations, slab grasping means on said carriage and means for displacingsaid grasping means vertically relative To said carriage so as to moveslabs successively into and out of said compartments, the improvementwherein said slab grasping means includes a unitary structure movable asa unit into and out of said basin and constituting two downwardlyopening pockets in parallel side-by-side relation, each for receiving atleast one of said slabs, and retaining means selectively operable upon asingle disposition of said grasping means in said basin to release a hotslab from one of said pockets into a vacant one of said compartments andto latch in the other of said pockets a cooled slab present in one ofsaid compartments adjacent to said vacant one.
 2. Apparatus according toclaim 1, said grasping means comprising a plurality of slab graspingdevices spaced apart transversely of said basin, each of said devicescomprising a central vertical bar and two outer vertical bars spacedhorizontally from said central bar, said bars defining said pocketstherebetween, said retaining means comprising on each of said outer barsa retaining member pivotally mounted for movement to and away from aclosed position in which said member extends across the bottom of andwill hold a slab in the related pocket.
 3. Apparatus according to claim2, said central bar having in the lower portion thereof a recess toreceive and a ledge to support an end portion of each of said retainingmembers.
 4. In apparatus for cooling metal slabs such as hot bars,billets, blooms or ingots, comprising an elongated basin for a coolingliquid, slab feeding and slab discharge stations respectively atopposite ends of said basin, means forming in and longitudinally of saidbasin a succession of upwardly open compartments each extendingtransversely of said basin for supporting therein a slab placedvertically therein, a carriage disposed transversely over said basin,means mounting said carriage for movement longitudinally of said basinbetween said stations, slab grasping means on said carriage and meansfor displacing said grasping means vertically relative to said carriageso as to move slabs successively into and out of said compartments, theimprovement wherein said slab grasping means constitute two downwardlyopening pockets in parallel side-by-side relation, each for receiving atleast one of said slabs, and retaining means selectively operable upon asingle disposition of said grasping means in said basin to release a hotslab from one of said pockets into a vacant one of said compartments andto latch in the other of said pockets a cooled slab present in one ofsaid compartments adjacent to said vacant one, said grasping meanscomprising a plurality of slab grasping devices spaced aparttransversely of said basin, eahc of said devices comprising a centralvertical bar and two outer vertical bars spaced horizontally from saidcentral bar, said bars defining said pockets therebetween, saidretaining means comprising a retaining member pivoted on an axis in saidcentral bar for rotation selectively to either of two working positionsin one of which said member extends across the bottom of and will hold aslab in one of said pockets and in the other of which it extends acrossthe bottom of and will hold a slab in the other of said pockets. 5.Apparatus according to claim 4, said retaining member being rotatableabout said axis in a substantially horizontal path of approximately 180*from one to the other of said positions, whereby a slab may be releasedfrom one of said pockets and another slab latched in the other of saidpockets by a rotation of said member.
 6. Apparatus according to claim 4,each of said outer bars having a recess therein to receive, and forminga ledge to support, the outer end portion of said retaining member. 7.The method of transporting metal slabs into and from a cooling basinwhich comprises a. moving a carriage having slab grasping means thereonin steps from a slab feeding station at one end of an elongate coolingbasin to the location of a vaCant compartment and an adjacentslab-containing compartment in a succession of slab cooling compartmentsprovided in and along said basin, next from said location to a slabdischarge station at the other end of said basin, and then back to saidfeeding station for a next series of such steps, said grasping meansconstituting two downwardly opening slab receiving pockets in parallelside-by-side relation; b. while said carriage is at said feeding stationplacing and latching a hot slab in one only of said pockets; c. whilesaid carriage is at said location; lowering said grasping means intosaid basin so as to place said hot slab in said vacant compartment andto place the other of said pockets in encompassing relation to a cooledslab in said slabcontaining compartment, then releasing said hot slabfrom said one pocket and latching said cooled slab in said other pocket,and then raising out of said basin said grasping means with only saidcooled slab held therein; and d. While said carriage is at saiddischarge station releasing said cooled slab from said other pocket.